An OFDMA (Orthogonal Frequency Division Multiplex Access: OFDMA, or OFDM-FDMA) communication system uses one of multiple access methods. In the OFDMA communication system, a base station constructs a cell and allocates at least one subcarrier to at least one mobile station that is included in the cell. Here, the sub-carriers allocated to the mobile stations are different from each other. According to the OFDMA communication system, it is possible to minimize intra-cell interference.
Meanwhile, a plurality of cells use a plurality of subcarriers in a general OFDMA communication system. At least one of the plurality of subcarriers used in a cell has the same index as that of other cells, and thereby interference (which will be called “Other Cell Interference: OCI) is generated by power of a neighboring mobile station positioned in a neighboring cell. Particularly, when a mobile station positioned at a boundary of a cell transmits signal having high transmission power with an allocated subcarrier to a base station, other cells except for the cell including the mobile station undergo interference influence. Therefore, an uplink control method for further controlling transmission power according to interference states of other cells is needed.
According to a general uplink control method of an OFDMA communication system, as shown in IEEE 802.20, a mobile station determines a plurality of monitoring sectors based on an amount of interference that has an effect on other cells. In addition, the mobile station may not use all of the plurality of monitoring sectors when controlling transmission power, and thus selects a monitoring sector to be used for the transmission power control from among the plurality of monitoring sectors through probability calculation. Here, there are few occasions in which the mobile station applies an interference amount of a monitoring sector to the transmission power control by the probability calculation using parameters of very small values. Therefore, according to the general uplink control method, even though interference has a great deal of effect on other sectors, it is unable to actively apply interference states of other cells to the uplink power control.
Further, according to the general method, a mobile station increases or reduces transmission power by a fixed threshold value based on an interference state of a monitoring sector to be applied to the uplink transmission power control, and the interference state is therefore not applied subsequently to the uplink transmission power control.
As described above, the general uplink power method includes a very complex calculation process, and thereby operation load of the mobile station increases.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.